Radio frequency fingerprinting to detect fraudulent radio frequency identification tags

Abstract

A method of authenticating the identity of an RFID device having a tag identifier stored therein. The tag identifier for the RFID device is recorded along with an RF fingerprint for the RFID device. When the RFID device is interrogated a response is received from the interrogated RFID device. An RF fingerprint is determined form the response and the received response including the RF fingerprint associated with the response is compared to an expected RF fingerprint previously known to be associated with the RFID device being interrogated.

1 . A method of authenticating the identity of an RFID device comprising the steps of: 
 providing an RFID device having a tag identifier stored therein;    recording the tag identifier for the RFID device along with an RF fingerprint for the RFID device;    interrogating an RFID device;    receiving a response from the interrogated RFID device;    determining an RF fingerprint for the received response; and    comparing the RF fingerprint associated with the received response to the RF fingerprint recorded with the tag identifier of the RFID device.    
   
   
       2 . The method of  claim 1  wherein the RF fingerprint is based on an amplitude component of a turn-on transient produced by the RFID device.  
   
   
       3 . The method of  claim 1  wherein the RF fingerprint is based on a phase component of a turn-on transient produced by the RFID device.  
   
   
       4 . The method of  claim 1  wherein the RF fingerprint is based on a frequency component of a turn-on transient produced by the RFID device.  
   
   
       5 . An RFID price tag implementing the method of  claim 1 .  
   
   
       6 . The method of  claim 1  further comprising: 
 determining the RF fingerprint by sequentially interrogating the RFID device a plurality of times, sampling the RF characteristics of the response signal from the RFID device; analyzing the response signal to identify at least one unique characteristic of the RF response; and calculating an RF fingerprint using the at least one characteristic.    
   
   
       7 . The method of  claim 1  further comprising maintaining a table storing the tag identifier for each of a plurality of RFID devices in association with an RF fingerprint for the RFID device.  
   
   
       8 . The method of  claim 1 , wherein the RFID device comprises a passive, unpowered circuit that transmits a unique ID in response to an interrogation signal.  
   
   
       9 . A system for authenticating RFID devices comprising: 
 a plurality of RFID devices, each having a tag identifier stored therein;    a data structure having a plurality of entries, wherein each entry is associated with a particular RFID device and holds the tag identifier for the associated RFID device along with an RF fingerprint for the associated RFID device;    a reader/interrogator operable to send an interrogation signal to the RFID devices, wherein at least one of the plurality of RFID devices is configured to generate a response signal in response to the interrogation signal;    a receiving component in the reader/interrogator operable to receive the response from one of the interrogated RFID devices;    a computational component in the reader/interrogator that is operable to determine an RF fingerprint for the received response; and    a lookup mechanism coupled to the data structure and operable to use information from the received response to retrieve an RF fingerprint associated with the RFID device; and    a comparator comparing the RF fingerprint associated with the received response to the RF fingerprint recorded with the tag identifier of the RFID device.    
   
   
       10 . The system of  claim 9  wherein the RF fingerprint stored in the data structure for a particular RFID device is determined by sequentially interrogating the RFID device a plurality of times, sampling the RF characteristics of the response signal from the RFID device; analyzing the response signal to identify at least one unique characteristic of the RF response; and calculating an RF fingerprint using the at least one characteristic.  
   
   
       11 . The system of  claim 9  wherein the RF fingerprint is based on an amplitude component of a turn-on transient produced by the RFID device.  
   
   
       12 . The system of  claim 9  wherein the RF fingerprint is based on a phase component of a turn-on transient produced by the RFID device.  
   
   
       13 . The system of  claim 9  wherein the RF fingerprint is based on a frequency component of a turn-on transient produced by the RFID device.  
   
   
       14 . The system of  claim 9  wherein the data structure is indexed by an identifier encoded in the RFID device, wherein the identifier is included in the response signal generated by the RFID device.  
   
   
       15 . A data structure implemented in a physical memory device for use in an RFID authentication system, the data structure comprising: 
 a plurality of entries, wherein each entry is associated with a particular RFID device;    an identifier value stored in each entry, wherein the identifier is the same as an identifier stored in the associated RFID device; and    an RF fingerprint stored in each entry, wherein the RF fingerprint has been determined from RF characteristics of the associated RFID device.    
   
   
       16 . The data structure of  claim 15  wherein the data structure is indexed by the identifier values.  
   
   
       17 . The data structure of  claim 15  further comprising an interface for receiving requests that identify a particular identifier value, initiating a lookup in the table to identify one or more entries associated with the particular identifier value, and returning one or more RF fingerprints from the identified one or more entries.